The anomaly occurred Oct. 4, when a Delta 4 rocket blasted the GPS IIF satellite safely into orbit. While the unmanned X-37B spacecraft is ready to fly and doesn't use the Delta 4 — it lifts off atop an Atlas 5 — the Air Force's investigation into the glitch may affect the space plane's launch schedule.

Air Force Space Command commander General William Shelton has asked for a discretionary accident investigation board (AIB) to investigate why the Delta 4 RL-10B-2 upper stage engine did not perform as expected during the GPS satellite launch, said USAF Major Tracy Bunko at the Pentagon’s Air Force Press desk.

The upcoming X-37B mission — also known as Orbital Test Vehicle-3 (OTV-3) — is currently slated to blast off Oct. 25 from Space Launch Complex 41 at Florida's Cape Canaveral Air Force Station.

The third mission of the X-37B also marks the first re-flight of one of the space planes. This same vehicle flew the first flight, called OTV-1, back in 2010.